The present invention is generally directed to the field of "Hot Box Detectors" which are used to determine whether the wheel bearings on railroad rolling stock are over-heating and, in particular, is directed to an improved system for insuring that such hot box detectors are operating properly.
Hot box detectors are well known. Hot box detectors comprise heat sensing scanners which are located at spaced points along railroad tracks. The scanners sense the temperature of wheel bearings of passing railroad equipment and, typically transmit the sensed temperature information to a telemetry unit. At the telemetry unit the sensed wheel bearing temperature is compared against a reference and if the reference temperature is exceeded an alarm is transmitted via the telemetry unit to the locomotive engineer.
Defective wheel bearings on railroad equipment are a particularly important problem. When the maximum operating temperature of a railroad wheel bearing is exceeded the wheel may crack thus causing a derailment. Derailments, in addition to being hazardous to crews and passengers, may also lead to the contamination of the environment due to the spilling of hazardous materials and the like. In order to eliminate and minimize derailments railroads typically employ "hot box detectors".
When a hot box detector senses an over-heated wheel bearing the locomotive engineer is expected to stop the train and determine whether the bearing, is indeed, over-heated. The stoppage of railroad traffic for this reason results in downtime for both freight and passengers. Accordingly, it is important that train stoppages for defective wheel bearings take place only when a defective wheel bearing condition has actually been determined. Conversely, it is important that all hot box detectors along a railroads trackage be operating properly. Defectively operating hot box detectors may permit trains having defective wheel bearings to proceed uninterrupted thus causing derailments and corresponding injuries and property damage.
Verification and maintenance of hot box detector is typically carried out by railroad employees who travel along the track periodically and who stop and verify hot box detectors along the route. Such maintenance and calibration procedures are labor intensive and expensive. More importantly, however, maintenance personnel ar able to check hot box detectors only under static conditions. Hot box detectors may appear to be operating properly under static conditions but may, in fact, fail to detect hot wheel bearings under the dynamic conditions created by passing trains.
It would be desirable to provide an apparatus for maintaining and verifying hot box detectors which monitors the operation of such detectors under dynamic conditions caused by the passage of a load along the railroad track.
Hot box detectors typically fall into two classes, namely rail-mount and ballast-mount types. Rail-mounted hot box detectors are mounted on the rail of a railroad track. Ballast mounted hot box detectors are located in the ballast adjacent the rail. The accuracy of both types of hot box detectors may be affected by the passage of a train along the rail. For this reason, dynamic testing of hot box detectors would be desirable.
One method of maintaining and verifying hot box detectors in a dynamic fashion has been proposed. In the proposed method a rolling railroad car is provided carrying a simulated heat source. The simulated heat source is maintained at a temperature far exceeding the temperature of a defective wheel bearing. As the car with the simulated heat source passes over the hot box detector, the simulated heat source causes the hot box detector to trip if the detector is operating. One problem associated with the proposed method is the fact that the simulated heat source is maintained at a temperature far exceeding the temperature of a defective wheel bearing. If a hot box detector trips when the simulated heat source passes the detector all that may be determined is that the hot box detector will trip. It cannot be determined, however, whether the hot box detector will trip when a defective wheel bearing passes. Another difficulty with the proposed method resides in the fact that the simulated heat source provides no compensation for changes in ambient temperature.
Hot box detectors must detect defective wheel bearings irrespective of changes in ambient temperature. On cold days the differential between ambient and defective bearing temperature is correspondingly larger than the differential on warm days. It would be particularly desirable to provide a means for maintaining and calibrating hot box detectors which compensates for changes in ambient temperature.
It would also be desirable to provide a means and method for maintaining and verifying hot box detectors which was not labor intensive.
It would also be desirable to provide a means and method for maintaining and verifying hot box detectors under dynamic load conditions.
It would also be desirable to provide a means and method of maintaining and verifying hot box detectors which accommodated for both rail mount and ballast mount type detectors.
It would also be desirable to provide a means and method for maintaining and verifying hot box detectors which precisely control the temperature of a hot box simulator irrespective of changes in ambient temperature.